catboost: add natsukium to maintainers

pkgs/development/libraries/catboost/default.nix

···
     license = licenses.asl20;
     platforms = platforms.unix;
     homepage = "https://catboost.ai";
-    maintainers = with maintainers; [ PlushBeaver ];
+    maintainers = with maintainers; [ PlushBeaver natsukium ];
     mainProgram = "catboost";
   };
 })